Holes must be drilled in various structures for many different purposes. For example, holes must frequently be drilled through structures so as to permit fasteners to subsequently be inserted through the holes in order to attach or join the structures. In one example, the assembly of an aircraft required thousands of holes to be drilled so as to permit fasteners to be installed in order to join the various components of the aircraft. In this regard, many holes must be drilled through the skin in order to install fasteners to connect the skin to doublers, stringers and other components of the frame of the aircraft. Similarly, holes must be drilled during the assembly process of other vehicles, as well as a wide variety of other structures including buildings, bridges and the like.
In a number of these applications, holes must be drilled through a plurality of different layers that have been stacked one upon another. During the assembly of an aircraft, for example, holes may be formed through the skin of the aircraft, a doubler, a stringer and/or a beauty strip as well as other components of the frame. In order for the holes through these multiple components to be aligned, it is advantageous, if not essential, that a single hole be drilled through the multiple components once the components have been stacked one upon another. Unfortunately, gaps often exist between the different layers of a multi-layer structure or are created during the process of drilling a hole through a multi-layer structure. While these gaps could otherwise generally be closed following the installation of a fastener through the hole, these gaps facilitate the formation of inter-laminar burrs about the periphery of the hole being formed. In addition, chips generated during the drilling operation may enter the gap and migrate through the gap away from the hole that has been formed. If not removed, these inter-laminar burrs and chips that have migrated within the gap would prove quite disadvantageous. For example, the inter-laminar burrs and chips trapped within the gaps may prevent fasteners that are subsequently installed in the holes from completely closing the gaps such that the resulting laminar structure continues to have gaps therein.
In those instances in which the multi-layer structure has not yet been fastened together, such as by fasteners inserted through holes defined by the multi-layer structure, the various components may be disassembled and cleaned in order to remove the burrs and chips. The cleaned components are then reassembled and aligned. In order to permit proper installation of fasteners through the multi-layer structure, the various components must be precisely aligned such that the holes that have been formed through the various components extend through the entire structure. As will be apparent, this process of disassembling, cleaning and reassembling a multi-layer structure following hole formation but prior to fastener installation is time consuming and increases the costs of the resulting structure. Moreover, in some instances, holes are drilled in a multi-layer structure that has already been fastened together, such as by fasteners joining other portions of the structure. In these instances, it is generally infeasible to disassemble the multi-layer structure and, as such, the resulting structure may disadvantageously include inter-laminar burrs and chips that have been introduced into the gaps during the process of drilling or otherwise forming holes therethrough.
It would also be desirable to provide a drill for forming holes in various structures, including multi-layer structures, that reduces, if not eliminates, the formation of inter-laminar burrs and the introduction and migration of chips through gaps within the structure. It would therefore be desirable to provide a drill capable of drilling holes through a multi-layer structure in such a way that gaps that may exist within the structure are reduced, if not eliminated, and that reduces, if not eliminates, the likelihood that additional gaps will be formed during the drilling process.